I could go into lengthy detail about the host licensing system I recently designed (which, if I know the people here, someone else has probably developed anyway), but the simplest answer is as Unknown Person said. Unless you put safeguards in, if it's already hosted all you can do is change the hub password so that it won't appear on your hub.

In addition to what both of the other two have said, you can use version checks as a safeguard. In Align Four, and if I recall, every other game I have out on the hub, I implemented a version check at world/New. It'd check world.version against the version on the hub. If they didn't match up, it'd delete the world. The only problem with this approach was that sometimes the version check would stop working and report the new version (world.version matching the version on the hub) as being outdated. I believe it has something to do with updating of the game, because the version check then worked correctly if I removed the game from my pager and added it again.

In addition to what both of the other two have said, you can use version checks as a safeguard. In Align Four, and if I recall, every other game I have out on the hub, I implemented a version check at world/New. It'd check world.version against the version on the hub. If they didn't match up, it'd delete the world. The only problem with this approach was that sometimes the version check would stop working and report the new version (world.version matching the version on the hub) as being outdated. I believe it has something to do with updating of the game, because the version check then worked correctly if I removed the game from my pager and added it again.

Oh yeah good point. I thought you could do that, but I wasn't sure of HOW to do it, so I didn't mention it. That's why you can't host DMO without it dying on you XD. Yeah, what Audero said is by far the easiest way of doing it.